Respiratory diseases resembling influenza has infected thousands of dogs in the U.S. Recurrent outbreaks of severe respiratory disease characterized by coughing and fever have occurred in greyhounds at racing kennels. Pathological findings included severe pulmonary and plural hemorrhage, accurate to subacute erosive to hyperplastic tracheitis, bronchitis and bronchiolitis and bronchopneumonia. In 2004, eight greyhounds in Jacksonville, Fla. were killed by an equine influenza virus that jumped the species barrier from horses to dogs.
Equine influenza is a disease of horses, and the virus is in the same group of viruses that cause flu in people. The disease is present in horse populations throughout Europe, North America and parts of Asia, with horses typically developing a fever and a dry hacking cough. In the early stages of the disease, horses are reluctant to eat or drink for several days, but usually recover in two to three weeks.
H3N8 subtypes of equine influenza were previously isolated from lungs of two dogs from Florida and one dog from Texas who had died from the infection. Genetic sequence analyses and phylogenetic comparisons determined that all three canine isolates were closely related and evolved from contemporary strains of equine influenza H3N8. Immunohistochemistry demonstrated influenza antigen in bronchial gland epithelial cells, bronchial and bronchiolar epithelial cells and in alveolar macrophages. Seroconversion to canine influenza virus was demonstrated by hemagglutination inhibition and microneutralization assays.
In 2005, a mutated form of the Bird Flu (H3N8 Virus) was reported to have killed greyhounds in Massachusetts.
Accordingly, there is a need for an effective vaccine against influenza in canines.
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